package cn.icatw.leetcode.editor.cn;
//给定一个二叉树，判断它是否是 平衡二叉树
//
//
//
// 示例 1：
//
//
//输入：root = [3,9,20,null,null,15,7]
//输出：true
//
//
// 示例 2：
//
//
//输入：root = [1,2,2,3,3,null,null,4,4]
//输出：false
//
//
// 示例 3：
//
//
//输入：root = []
//输出：true
//
//
//
//
// 提示：
//
//
// 树中的节点数在范围 [0, 5000] 内
// -10⁴ <= Node.val <= 10⁴
//
//
// Related Topics 树 深度优先搜索 二叉树 👍 1528 👎 0


//Java：平衡二叉树
public class T110_BalancedBinaryTree {
    public static void main(String[] args) {
        Solution solution = new T110_BalancedBinaryTree().new Solution();
        // TO TEST
    }
    //leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     * int val;
     * TreeNode left;
     * TreeNode right;
     * TreeNode() {}
     * TreeNode(int val) { this.val = val; }
     * TreeNode(int val, TreeNode left, TreeNode right) {
     * this.val = val;
     * this.left = left;
     * this.right = right;
     * }
     * }
     */
    class Solution {
        public boolean isBalanced(TreeNode root) {
            return height(root) >= 0;
        }

        private int height(TreeNode root) {
            if (root == null) {
                return 0;
            }
            int leftHeight = height(root.left);
            int rightHeight = height(root.right);
            if (leftHeight == -1 || rightHeight == -1 || Math.abs(leftHeight - rightHeight) > 1) {
                return -1;
            }
            return Math.max(leftHeight, rightHeight) + 1;
        }
    }

    //leetcode submit region end(Prohibit modification and deletion)
    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {
        }

        TreeNode(int val) {
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
}
